Evaluation of the antihypertensive activity and alpha adrenergic receptor interaction of cleistanthins A and B.

Hypertension was induced in male Sprague Dawley rats with twice weekly administration of deoxycorticosterone acetate (DOCA) salt (20 mg/kg s.c) for 4 weeks. They were divided into eight groups of six animals each viz., hypertensive control, standard (prazosin 1 mg/kg), cleistanthin A 12.5, 25, 50 mg/kg and cleistanthin B 12.5, 25 mg/kg, and 50 mg/kg. One more group served as normal control. The hypertension was induced in 4 weeks, and the animals were given assigned treatment in 5(th) week. The alteration in blood pressure (BP) was recorded weekly using a rodent noninvasive blood pressure system. At the end of the experiment alpha-adrenergic receptor response of drugs like adrenaline, nor adrenaline, dopamine (doses 1 μg and 2 μg) was recorded invasively. Two-way repeated measures ANOVA followed by Bonferroni post-hoc test was used to analyze the data. The systolic BP and diastolic BP of test groups rose to a higher level after DOCA administration and fell to the normal range (P < 0.05) following the administration of cleistanthins A and B. There were no differences in the weekly heart rate among the groups. In the test group animals pretreated with prazosin and cleistanthins, adrenaline, noradrenaline and dopamine failed to raise the mean arterial pressure and the end-diastolic pressure from baseline (P > 0.05) cleistanthins A and B exert a significant antihypertensive effect through alpha-adrenergic receptor blockade similar to prazosin.